Laura “Lo” Blacklock, a 32-year-old travel journalist, is trapped in the bedroom of her London flat one night while a burglar ransacks her belongings. After breaking her way out, she struggles with flashbacks and insomnia, but she’s determined not to miss her big break: covering the Aurora, a luxury yacht cruising the Norwegian fjords to see the northern lights, for the travel magazine Velocity. Before leaving for the cruise, she argues with her boyfriend, Judah, because she’s hesitant to move forward in their relationship, despite Judah waiting for months and turning down a New York job offer to stay with her.
By the time she’s welcomed aboard the Aurora, Lo is severely sleep-deprived and still suffering flashbacks to the burglary. She also uses alcohol to help her manage her anxiety. On the first evening of the cruise, Lo knocks on the door of the neighboring cabin to borrow some mascara. She’s greeted by a surprised young woman wearing a ratty Pink Floyd T-shirt. The woman seems flustered and abruptly shuts the door in her face after giving her the mascara.